The present invention relates to a new and improved coupling assembly and more specifically to a coupling assembly which has a stationary housing section which at least partially encloses a clutch assembly and a brake assembly.
A known coupling assembly is disclosed in U.S. Pat. No. 5,257,684 issued Nov. 2, 1993 and entitled "Coupling Assembly". This known coupling assembly includes a clutch assembly which is operable between an engaged condition and a disengaged condition. When the clutch assembly is in the engaged condition, it is effective to transmit force from an input member to an output member. When the clutch assembly is in a disengaged condition, it is ineffective to transmit force from the input member to the output member.
In addition, the known coupling assembly includes a brake assembly. The brake assembly is operable between an engaged condition and a disengaged condition. When the brake assembly is in the engaged condition, it is effective to hold the output member against rotation. When the brake assembly is in the disengaged condition, it is ineffective to hold the output member against rotation.
An actuator assembly for operating the brake and clutch assemblies in the known coupling assembly disclosed in the aforementioned U.S. Pat. No. 5,257,684 includes a piston which rotates with the output member when the clutch assembly is in an engaged condition. The piston adds to the rotary mass of the coupling and thereby adds to the rotational inertia of the coupling. Since the piston rotates when the clutch assembly is engaged, a rotary seal arrangement must be provided to conduct fluid to a rotating cylinder chamber associated with the piston.
During rotation of the known coupling assembly with the clutch assembly engaged, centrifugal force contributes to a fluid pressure head which tends to maintain the clutch assembly in an engaged condition. In order to overcome the pressure head, relatively strong springs must be provided to effect movement of the piston and operation of the clutch assembly to a disengaged condition. However, since the fluid pressure head increases as an exponential with rotational speed, the strength of the springs tends to limit the rotational speed at which the coupling can be utilized.